The above description represents the typical configuration of a watercraft device known as “SWATH”, an acronym of “Small Waterplane Area Twin Hull.”
These vessels are made of a watercraft that generally has two lateral hulls, representing the above mentioned Twin Hulls, which are submerged below the free surface so that the waterline figure is reduced. This area reduction allows reducing the motions and sustaining speed in waves of the SWATH for a given power, inasmuch as the variation of displaced volume by the total SWATH due to an incoming wave is also reduced.
The SWATH device of this patent has been studied to be particularly used as an autonomous surface vehicle, to perform offshore environment measurements and monitoring, as well as to launch recovery and maintenance of underwater devices (generally autonomous also), those underwater devices being also used for monitoring seabed and water conditions or other kind of missions, as for example, mine detection.
Unlike conventional catamarans, in SWATH devices, during navigation, lateral hulls are completely maintained below the water surface, so that they are less influenced by wave actions, because the force exerted by the waves on submerged structures decreases exponentially with increasing depth.
Therefore, the shift of both hulls below sea level gives SWATH devices a better seakeeping in sea waves than conventional devices and catamarans. This is why SWATH devices are particularly suited for use in offshore operations, either manned or unmanned, as autonomous vehicles.
Despite high stability in sea waves provided by the above described configuration, SWATH devices have the disadvantage of higher propulsion powering requirements, especially at high speeds and hence have higher fuel consumptions. In fact, compared to equivalent mono-hulls or catamarans, these devices experience more drag when moving at a given speed in calm water or, conversely, with a given propulsion power they reach a lower speed. This is due to the higher wetted surface of the SWATH watercraft and to its higher wave resistance (related to the wave formation generated by the hull advancing at steady speed in calm water) of the submerged hulls, if these hulls have conventional (traditional) shape, that is, a shape not properly modeled according to the present invention.
Therefore, there is an unmet need to realize a floating device, which can operate without personnel on board, preferably of a SWATH type; which can reach a high platform stability in relatively high sea states with simple and inexpensive devices; and which at the same time can reach higher speeds than the state of the art SWATH devices, ensuring a low fuel consumption that is at least comparable if not lower than the traditional hulls of equivalent size and capacity.